|Publication number||US7091615 B2|
|Application number||US 11/084,638|
|Publication date||Aug 15, 2006|
|Filing date||Mar 18, 2005|
|Priority date||Aug 31, 2001|
|Also published as||US6887780, US20030042605, US20050161827|
|Publication number||084638, 11084638, US 7091615 B2, US 7091615B2, US-B2-7091615, US7091615 B2, US7091615B2|
|Inventors||Ebrahim Andideh, Mark Bohr|
|Original Assignee||Intel Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (33), Non-Patent Citations (5), Classifications (27), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present patent application is a Divisional of application Ser. No. 09/943,874, filed Aug. 31, 2001, now U.S. Pat. No. 6,887,780.
1. Field of the Invention
The present invention relates to low k dielectrics, and more particularly, to a carbon doped oxide having a carbon doping concentration that is graded.
2. Background Information
As integrated circuit technology advances, integrated circuit devices become smaller and smaller. This allows for greater speed and increased device packing densities. Sizes of individual features, for example the transistor gate length, on modern integrated circuits is shrinking to less than 50 nanometers. The resultant increase in packing densities has greatly increased the number and density of metal interconnects on each chip.
The metal interconnects (which consist of conducting lines and vias) have become smaller, more complex, and more closely spaced. The smaller sizes of the interconnect pitch leads to RC (resistance-capacitance) coupling problems which include propagation delays and cross talk noise between interlevel and intralevel conductors. RC delays thus limit improvement in device performance. Additionally, fringing electrical field effects near the metal lines may adversely affect performance of the interconnects.
Capacitance can be reduced by employing low dielectric constant (low k) dielectric materials to insulate the metal interconnect lines. Since capacitance is directly proportional to the dielectric constant of the insulating material, the RC delay can be reduced when a low k material is used. Various semiconductor equipment manufacturers have developed low k dielectrics. One of the most promising low k dielectrics is the carbon-doped oxide (SiOxCyHz).
While carbon doped oxide (CDO) film has been found useful to reduce capacitance by lowering film density and polarizability of bonds, CDO film has poor thermal and mechanical properties. For example, CDO exhibits poor hardness, is susceptible to cracking, and has low thermal conductivity.
The foregoing aspects and many of the intended advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The present invention describes a method for forming a carbon doped oxide (CDO) film having a graded concentration of carbon doping. In one embodiment, the CDO film is utilized for interlayer dielectric applications.
In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
Reference throughout this specification to “one embodiment”, “preferred embodiment”, or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment”, “in a preferred embodiment”, or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Further, typically, the CDO layer 105 is patterned and etched in accordance with a desired via pattern. The carbon-doped oxide layer 105 is etched to form vias 107 in the carbon-doped oxide layer 105. In the prior art, the CDO layer 105 has a homogenous concentration of carbon dopants. This can be seen in
In accordance with the present invention, the carbon dopant concentration is graded. Specifically, in those regions of the CDO layer 105 that are proximal to the metal interconnect 103, a high carbon dopant concentration is provided. This lowers the k value of the CDO layer. In those regions of the CDO layer 105 that are distal to the metal interconnect 103, e.g., between the vias 107, a relatively low carbon dopant concentration is provided. This increases the hardness and increases cracking resistance and thermal conductivity of the CDO layer 105.
Specifically, turning to
The advantage of such a CDO layer 205 is that proximal to the metal interconnect 203, a high carbon dopant concentration is present. This lowers the dielectric constant, thereby reducing electrical field fringe effects and capacitance. Proximal to the vias 207, where capacitance issues and fringe effects are not as pronounced, the carbon dopant concentration is lower. In the region proximal the vias 207, the CDO layer 205 has enhanced hardness, greater resistance to cracking, and greater thermal conductivity, relative to the CDO layer 205 proximal the metal interconnect 203.
The present invention can also be applied to dual damascene type structures. For example, turning to
As seen in
By having the lower carbon dopant concentration adjacent to the via portion of the opening 307, enhanced hardness, thermal conductivity, and resistance to cracking is provided. Note that in the upper region of the openings 307 (carrying the second metal interconnect structure), a higher carbon dopant concentration is provided. This reduces the dielectric constant and provides the advantages noted above. Thus, in this embodiment, the higher dopant concentration is near the surface of the CDO layer 305 and the lower concentration of dopant is provided near the bottom of the CDO layer 305.
In an alternative embodiment, referring to
Still alternatively, referring to
In one embodiment, the carbon dopant concentration ranges from 1–20% (by atomic mass) for the carbon dopant. Thus, for low carbon dopant concentration regions, 1% carbon dopant is provided. For high carbon dopant regions, up to and over 20% carbon dopant concentration may be used. However, it can be appreciated that other dopant concentrations may be used, customized for the specific application.
The formation of variably doped CDO is described in relation to
For example, turning to
It should be noted that while four specific examples of gases that can be used to form the CDO layer have been described above, numerous other techniques may be used to form CDO. The present invention teaches that, contrary to the prior art, a CDO layer can be formulated having a variable carbon dopant concentration. While in one embodiment, the carbon dopant concentration can be varied in situ to improve throughput, as well as to provide a smooth transition between carbon dopant concentrations, discreet layers of CDO having varying carbon dopant concentrations may also be used to formulate a bulk interlayer dielectric. Moreover, the placement of the high and low carbon dopant concentrations is variable dependent upon the types of structures being formed and the types of capacitance and electrical fringing effects present. Thus, while specific examples of dopant concentration profiles have been provided, these dopant profiles are not meant to be limiting.
Thus, while several specific embodiments of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
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|U.S. Classification||257/760, 257/E21.277, 257/E23.154, 257/E21.579, 257/E23.144, 257/E23.167, 257/E21.576|
|International Classification||H01L23/532, H01L21/768, H01L21/316|
|Cooperative Classification||H01L23/53295, H01L21/31633, H01L2924/0002, H01L21/02126, H01L21/76822, H01L23/5329, H01L21/76801, H01L21/76807, H01L21/02274|
|European Classification||H01L21/02K2E3B6B, H01L21/02K2C1L1, H01L21/768B, H01L21/768B2D, H01L21/316B8, H01L23/532N4, H01L23/532N, H01L21/768B8|
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